help please for question for city and guilds exam coming up

[camerondurance]

please can any one help me with some questions on my pre exam papers struggling with

Q1 a load of 2.5kW connected to a 230V single phase supply draws a current of 12A calculate the power factor of the load?

Q2 currents on a 3 phase star connected load are I brown 50A I blue 70A and I grey 35A. determine the currently in the neural either by calculation or using a phasor diagram ?

Hope some one can help me really struggling with these 2

 

[SPECIAL LOCATION]

I very much doubt you are going to get spoon-fed answers without first trying to answer yourself and show you working....?


As this is the way things worked back in the day when I did my training:-

Tutor sets question...
You have a go at answering...
Discuss your answer with tutor to establish if you were right or wrong.. and/or where you went wrong with your calculations..
Thus you learn from your mistakes..

The method of Tutor set question...
Then tells you the answer, without giving you a chance to answer first, never really helps anyone!

 

[binky]

give it a stab on here, and those who know will point out where you are going wrong. NB no good asking me as I've forgotten how to do those calculations due to never using them for many years.

 

[johnb2713]

please can any one help me with some questions on my pre exam papers struggling with
Q2 currents on a 3 phase star connected load are I brown 50A I blue 70A and I grey 35A. determine the currently in the neural either by calculation or using a phasor diagram ?

The formula to find the neutral current is the square root of the following: (L1^2 + L2^2 + L3^2 – L1L2 – L1L3 – L2L3).

Power Factor is black magic and I avoid at all costs.

 

[Sparkless]

To answer Q1
What would the current be if the load were purely resistive?
The difference between this and the stated current is due to reactance in the load.
Comparing the 2 currents using a vector diagram will give you the power factor.

 

[poni]

 

[binky]

View attachment 16291

Any explanation that involves beer is good for me

 

[SPECIAL LOCATION]

Any explanation that involves beer is good for me

Still trying to remember if the guidance was.......

Have a beer:- After / Before / During an exam....



Or was it ALL three????

 

[kerching]

Have the beer instead of the exam!
Works for me
Never done an exam in my life